JP2018065120A - Water treatment apparatus and its method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a water treatment apparatus and its method, capable of performing an immersion-type filtration stably at a low cost, even when the quality of raw water fluctuates.SOLUTION: The water treatment apparatus 100 comprises: a water tank 3 for receiving raw water; a membrane module 4 stored and immersed in the water tank 3 for filtration treatment to make filtrate water; a drain channel 10 capable of draining water retained in the water tank 3; a flow regulating device P2 capable of regulating the flow rate of the water drained from the drain channel 10; a water quality sensor 2 for measuring the quality of the raw water; and a controlling unit 20 for controlling the flow regulating device P2 based on the measurement by the water quality sensor 2. The water treatment method comprises filtration treatment of raw water by utilizing the difference of water level while draining the water retained in the water tank 3 to increase the flow rate of the retained water drained from the drain channel 10 when an amount of a suspended substance contained in the raw water increases.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a water treatment apparatus and a water treatment method for purifying raw water by membrane filtration.

  In water purification, raw water taken from a water source is treated to remove turbidity, disinfecting, etc., and drinking water is produced. Further, in addition to turbidity removal treatment and disinfection treatment, advanced water purification treatment such as activated carbon treatment, ozone treatment, and biological treatment may be combined to reduce harmful substances and odors. Conventionally, slow filtration, rapid filtration, coagulation sedimentation, and the like have been used as a process for removing turbidity, but in recent years, a filtration process by membrane filtration based on a membrane separation method has also been widely used. .

  Membrane filtration uses membrane modules equipped with microfiltration membrane (MF membrane), ultrafiltration membrane (UF membrane; Ultrafiltration Membrane), etc., and mass transfer by transmembrane differential pressure on the separation membrane Is driven. Membrane separation devices that perform membrane filtration include a pressure type that supplies pressurized raw water to the primary side of the separation membrane to generate a transmembrane pressure difference, or a membrane module that is immersed in water, and the secondary side of the separation membrane is There is an immersion type that generates a transmembrane pressure difference at a low pressure.

  In the submerged membrane separation apparatus, raw water is introduced and stays in a water tank in which the membrane module is immersed in water, and the filtered water is made by flowing the retained water into the membrane module and performing membrane filtration. There are two methods for driving membrane filtration using a submerged membrane separator: a method in which stagnant water is pumped from the secondary side of the separation membrane, or a water level difference is provided on the secondary side of the separation membrane, and the permeated water is gravity filtered. There is a way to do it.

  For example, Patent Document 1 discloses an apparatus having a configuration in which a filtration separation tank in which a filtration module is immersed is provided, and filtered water is obtained from the filtration module by a water level difference. Washing waste water containing SS (suspended solids) is supplied to the filtration separation tank in which the filtration module is immersed, and SS is separated by the filtration module.

JP 2004-141771 A

  As disclosed in Patent Document 1, an immersion type membrane separation apparatus that performs membrane separation utilizing a water level difference does not require special power to generate a transmembrane pressure difference, and thus operates at a low power cost. Is possible. For example, a water treatment device that purifies the raw water taken by membrane filtration will continue to produce filtered water at a high recovery rate even if the operating pressure is low, as long as the raw water taken from the water source is clear and normal. Is possible. Therefore, this type of water treatment apparatus is desired to have a performance capable of continuing membrane filtration only with a pressure difference due to the water level without using power from the viewpoint of lowering the operating cost.

  However, the raw water to be filtered may vary in water quality due to the weather at the water source, pretreatment after water intake, etc., and the amount of turbidity may increase suddenly. If the amount of turbidity contained in the raw water increases, the separation membrane will become clogged and the permeation resistance will increase.Therefore, the separation membrane will be damaged due to high pressure load, or only by the pressure difference due to the water level. There is a problem that it is difficult to continue the membrane filtration.

  For such a problem, it is possible to lower the operating pressure of the membrane module by lowering the recovery rate of filtered water to be produced. However, when such measures are taken, it is necessary to lengthen the operation time of the water treatment apparatus when producing a certain amount of filtered water. When the operation time of the water treatment apparatus becomes longer, the total amount of raw water taken up and the total amount of accumulated water drained by turbidity concentrated by membrane filtration also increase, so that the operating cost of the water treatment apparatus increases.

  Alternatively, it is possible to cope with such a problem by providing a sufficient water level in the water treatment apparatus in advance so that the membrane filtration can be driven with a high water level difference. For example, if a sufficient height difference is provided between the water tank in which the membrane module is immersed and the filtered water tank that receives the freshly filtered water, the pressure difference due to the water level increases, so that a high operating pressure can be secured. However, when such measures are taken, it is difficult to pump the filtered water produced up to the height of the membrane module and backwash the separation membrane using the filtered water. May be higher.

  Therefore, an object of the present invention is to provide a water treatment apparatus and a water treatment method capable of stably performing submerged membrane filtration at a low cost even when the quality of raw water varies.

  In order to solve the above-mentioned problems, a water treatment apparatus according to the present invention includes a water tank into which raw water is introduced, and a membrane module that is held in the water tank soaked in water and that filters the raw water to produce filtered water. A drainage channel capable of draining the stagnant water staying in the water tank, a flow rate adjusting device capable of adjusting a flow rate of the stagnant water drained through the drainage channel, a water quality sensor for measuring the quality of the raw water, A control unit that controls the flow rate adjusting device based on measurement by a water quality sensor, and the control unit is preset with the amount of turbidity contained in the raw water that is obtained by measurement by the water quality sensor. When the first threshold value is reached, the flow rate of the accumulated water drained through the drainage channel is increased.

  Moreover, the water treatment method according to the present invention includes a water tank into which raw water is introduced, a membrane module that is immersed in water in the water tank, and performs filtration treatment of the raw water to produce filtered water, and the water tank. In a water treatment device comprising a drainage channel capable of draining stagnant stagnant water, the raw water is filtered using the difference in water level while draining stagnant water stagnating in the water tank, and is contained in the raw water When the amount of turbidity increases, the flow rate or drainage time of the accumulated water drained through the drainage channel is increased.

  ADVANTAGE OF THE INVENTION According to this invention, even if the water quality of raw | natural water fluctuates, the water treatment apparatus and water treatment method which can perform immersion type membrane filtration stably at low cost can be provided.

It is a schematic diagram which shows schematic structure of the water treatment apparatus which concerns on one Embodiment of this invention. It is a flowchart which shows the operation method regarding the stagnant water of the water treatment apparatus which concerns on one Embodiment of this invention. It is a flowchart which shows the operating method regarding the filtered water of the water treatment apparatus which concerns on one Embodiment of this invention. It is a flowchart which shows the other example of the operating method regarding the filtered water of the water treatment apparatus which concerns on one Embodiment of this invention. It is a schematic diagram which shows schematic structure of the water treatment apparatus which concerns on the modification of this invention. It is a flowchart which shows the operating method regarding the stagnant water of the water treatment apparatus which concerns on the modification of this invention.

  Hereinafter, a water treatment apparatus and a water treatment method according to an embodiment of the present invention will be described. In addition, about the structure which is common in each following figure, the same code | symbol is attached | subjected and the overlapping description is abbreviate | omitted.

Drawing 1 is a mimetic diagram showing a schematic structure of a water treatment equipment concerning one embodiment of the present invention.
As shown in FIG. 1, a water treatment apparatus 100 according to this embodiment includes a raw water channel 1, a turbidity sensor (water quality sensor) 2, a membrane separation tank (water tank) 3, a membrane module 4, and an air supply pipe 5. , Blower b1, filtered water flow rate sensor 6, filtered water flow rate adjustment valve (flow rate adjustment valve) 7, filtered water channel 8, filtered water pump P1, drainage flow rate sensor 9, drainage channel 10, and drainage pump (Flow control device) P2, filtration water tank 12, backwash water supply pipe 13, backwash pump P3, deaeration tank 14, deaeration pipe 15, vacuum pump P4, and controller 20 are provided. ing.

  The water treatment apparatus 100 is an apparatus that filters raw water that may contain turbidity by an immersion type membrane separation apparatus (membrane module 4) that performs membrane filtration using a difference in water level. As raw water, for example, pre-treatment such as water taken from a water source, coagulation sedimentation treatment for coagulating turbidity, demetallation treatment for removing metals such as iron and manganese, softening treatment for softening hard water, etc. Water is used. As the source of raw water, for example, rivers, lakes, groundwater, industrial water, irrigation water, domestic water and the like are used.

  Raw water is introduced into the membrane separation tank 3 through the raw water channel 1 from a water source or pretreatment equipment. The raw water channel 1 is provided with a turbidity sensor 2 for measuring the turbidity of the raw water, and the amount of turbidity contained in the raw water is measured by the turbidity sensor 2. In the water treatment apparatus 100, the filtered water pump P1, the drainage pump P2, and the blower b1 are controlled according to the amount of turbidity contained in the raw water, and the maintenance of the operating pressure of the membrane module 4 and the difference in water level are controlled. Utilization is planned.

  The membrane separation tank 3 contains a membrane module 4. The raw water introduced into the membrane separation tank 3 stays temporarily while maintaining the water level in the tank, and the membrane module 4 is held in a state immersed in water in the membrane separation tank 3. The raw water (residual water) staying in the membrane separation tank 3 is filtered by flowing into the membrane module 4. The membrane separation tank 3 may be either an open type or a closed type. The membrane module 4 may contain a single device or a plurality of devices in the membrane separation tank 3.

  The membrane module 4 is a membrane separation device that produces filtered water in which raw water is filtered to reduce the amount of dissolved substances. The membrane module 4 includes, for example, a separation membrane for membrane filtration having micropores, a water collection pipe for collecting filtered water produced through the separation membrane, and a support material for supporting the separation membrane and the water collection pipe. It is prepared for. The membrane module 4 may be either a cross flow filtration type or a dead end filtration type. As the separation membrane, a microfiltration membrane or an ultrafiltration membrane is usually provided.

  The separation membrane provided in the membrane module 4 is formed of, for example, an organic membrane such as cellulose acetate, nitrocellulose, polyamide, polyethylene, polypropylene, polysulfone, or an inorganic membrane such as alumina, zirconia, or glass. The separation membrane is in an appropriate form such as a hollow fiber type, a flat membrane type, or a tube type. As a method for incorporating the separation membrane, an appropriate method such as a sheet type, a spiral type, a tubular type, or a monolith type can be used according to the form of the separation membrane.

  The membrane module 4 is in contact with the staying water in the tank on the primary side of the separation membrane, and has an outlet through which filtered water filtered by the separation membrane flows out at the upper end. The outlet at the upper end communicates with a filtration water channel 8 for collecting the filtrate produced by the membrane module 4. The filtered water channel 8 connects between the membrane module 4 and the filtered water tank 12, and the filtered water made to permeate the secondary side of the separation membrane flows toward the filtered water tank 12. Yes.

  At the lower part of the membrane module 4, an air diffuser 5 a to which an air supply pipe 5 is connected is provided. The air supply pipe 5 is provided with a blower b1 for supplying air, and the membrane surface of the separation membrane provided in the membrane module 4 is physically cleaned (air scrubbing) by aeration. By performing the air scrubbing, turbidity adhering to the membrane surface of the separation membrane is peeled off, and accumulation of turbidity on the membrane surface is suppressed. Therefore, clogging of the separation membrane is difficult to occur, and an increase in the operating pressure of the membrane module 4 is suppressed. The membrane module 4 is not limited to the immersion type as described above, and it is also possible to use a pressurizing type in which the membrane module is housed in a casing and the casing is pressurized to obtain permeated water.

  The filtration water channel 8 includes a deaeration tank 14. The deaeration tank 14 is a processing tank for separating and removing the gas mixed in the filtered water. The deaeration tank 14 is connected to a deaeration pipe 15 provided with a vacuum pump P4. The deaeration tank 14 collects the gas mixed in the filtered water, is decompressed by the vacuum pump P4, and the gas mixed in the filtered water is removed by air scrubbing or the like.

  Moreover, the middle part of the filtrate water channel 8 is branched to form a double-lined channel (shown by a broken line in FIG. 1), and a filtrate water flow rate adjusting valve 7 and a filtrate water pump are provided in each middle part. P1. The filtered water flow rate adjusting valve 7 is provided so that the flow rate of the filtered water flowing through the filtered water channel 8 can be adjusted. On the other hand, the filtered water pump P1 is provided so that the filtered water flowing through the filtered water channel 8 can be pumped toward the filtered water tank 12. A filtered water flow rate sensor 6 is installed in the filtered water channel 8 so that the flow rate of the filtered water recovered from the membrane module 4 is measured.

  The filtered water tank 12 is a tank that receives the filtered water produced by the membrane module 4. The filtered water tank 12 is located at a lower height than the membrane separation tank 3, and the water level due to the height difference is provided with respect to the membrane separation tank 3. As the difference in height between the filtered water tank 12 and the membrane separation tank 3, for example, when the retained water staying in the tank of the membrane separation tank 3 is the lowest water level, the filtered water received by the accumulated water and the filtered water tank 12 A water level difference is generated between the water and the height at which the membrane filtration can be driven only by the water level difference without using power.

  The membrane separation tank 3 is connected to a drainage channel 10 provided with a drainage pump P2. The drainage channel 10 is provided so that the accumulated water staying in the membrane separation tank 3 can be drained by the operation of the drainage pump P2. On the other hand, the drainage pump P <b> 2 is provided so that the flow rate of the accumulated water drained through the drainage channel 10 can be adjusted. When the drainage pump P2 draws out the staying water remaining in the membrane separation tank 3, the turbidity concentrated in the membrane separation tank 3 by the membrane filtration is discharged, and the increase in the operating pressure of the membrane module 4 is suppressed. A drainage flow rate sensor 9 is installed in the drainage channel 10, and the flow rate of accumulated water drained from the membrane separation tank 3 is measured. In addition, instead of the drainage pump P2, the automatic drain valve 10 can be provided with an automatic valve in the drainage channel 10, and a natural flow method using the water level of the membrane separation tank can be adopted. In the case of an automatic valve, drainage is performed by opening and closing the valve.

  The flow rate of filtered water flowing through the filtered water channel 8 is adjusted to a predetermined flow rate by adjusting the opening of the filtered water flow rate adjustment valve 7 during normal operation of the water treatment apparatus 100. By adjusting the flow rate of the raw water and the flow rate of the filtered water, the water level of the membrane separation tank 3 is maintained, and an appropriate water level difference is maintained between the membrane separation tank 3 side and the filtered water tank 12 side. Due to the pressure difference due to the water level, the accumulated water flows into the membrane module 4 and is filtered. In addition, the freshly filtered water naturally flows down toward the filtered water tank 12 through the filtered water channel 8.

  The separation membrane provided in the membrane module 4 is back-washed with filtered water produced by the membrane module 4 or filtered water to which membrane cleaning chemicals are added. A backwash water supply pipe 13 equipped with a backwash pump P3 is connected to the filtered water tank 12. The backwash water supply pipe 13 connects the membrane module 4 and the filtrate water tank 12 by bypassing the filtrate water flow rate adjusting valve 7 and the filtrate water pump P1. The backwash pump P3 is provided so that backwashed filtered water can be pumped from the filtered water tank 12 to the secondary side of the separation membrane provided in the membrane module 4.

  The control unit 20 includes a CPU, a ROM, a RAM, a storage device, and the like. The control unit 20 has a function of controlling the filtrate flow rate adjusting valve 7, the blower b1, the filtrate water pump P1, the drainage pump P2, the backwash pump P3, etc., and executes various processes according to a predetermined operation program, The operation of the water treatment apparatus 100 is controlled. For example, a turbidity sensor 2, a filtrate water flow sensor 6, a drainage flow sensor 9, a water level sensor (not shown) that measures the water level of the membrane separation tank 3, and a pressure (not shown) that measures the pressure on the primary and secondary sides of the separation membrane Based on the measurement by the pressure sensor or the like, the state of the membrane separation tank 3 or the membrane module 4 is monitored, and the opening degree of the filtrate flow rate adjusting valve 7, the blower b1, the filtrate water pump P1, the drainage pump P2, and the backwash pump P3 Controls output during start, stop, and operation.

  Next, based on a specific operation method of the water treatment apparatus 100, a water treatment method according to an embodiment of the present invention will be described.

  The water treatment apparatus 100 is operated so that the filtration process by the membrane module 4 and the backwash process for backwashing the membrane module 4 are alternately repeated every predetermined time. During normal operation in which filtration is performed, raw water is introduced into the membrane separation tank 3 at a predetermined flow rate, and the raw water is filtered using the difference in water level while maintaining the retained water staying in the membrane separation tank 3 at a predetermined level. . On the other hand, during the backwash operation in which the backwash process is performed, the accumulated water staying in the membrane separation tank 3 is drawn out and drained at a predetermined flow rate, and the amount of turbidity concentrated in the membrane separation tank 3 is reduced.

FIG. 2 is a flowchart showing an operation method related to staying water in the water treatment apparatus according to the embodiment of the present invention.
As shown in FIG. 2, in the water treatment apparatus 100, the amount of turbidity contained in the raw water (raw water turbidity TU) is measured during normal operation in which the membrane module 4 performs filtration, and the membrane module 4 is reversed. The flow rate of the stagnant water that is drawn out and drained from the membrane separation tank 3 during the backwash operation for washing (drainage withdrawal amount F1) is adjusted based on the amount of turbidity contained in the raw water (raw water turbidity TU). Further, based on the amount of turbidity contained in the raw water (raw water turbidity TU), the operation of the blower b1 for air scrubbing the membrane module 4 is controlled.

  The control unit 20 starts the introduction of new raw water toward the membrane separation tank 3 according to a command from the operator or the operation program, and starts a normal operation in which the membrane module 4 performs a filtration process (Step S11). At the start of normal operation, the filtered water flow rate adjustment valve 7 is opened at an arbitrary initial opening. On the other hand, the filtered water pump P1 and the drainage pump P2 are stopped.

  Then, the control unit 20 measures the amount of turbidity (raw water turbidity TU) contained in the raw water introduced into the membrane separation tank 3 while the raw water is introduced into the membrane separation tank 3 (Step turbidity TU). S12). The amount of turbidity contained in the raw water (raw water turbidity TU) is measured at a predetermined cycle by the turbidity sensor 2 and input to the control unit 20.

  Next, the control unit 20 determines whether or not the blower b1 is operating (step S13). The blower b1 is in an activated state when the backwash operation is performed before the current normal operation and the air scrubbing is performed during the previous backwash operation. On the other hand, when air scrubbing is not performed during the previous backwash operation, the vehicle is stopped.

  If the blower b1 is not operating in step S13 (step S13; NO), the control unit 20 advances the process to step S16.

  On the other hand, if the blower b1 is operating in step S13 (step S13; YES), the control unit 20 advances the process to step S14.

  Next, the control unit 20 determines whether or not the amount of turbidity contained in the raw water (raw water turbidity TU) is less than a preset threshold (Th3) (step S14). As the threshold value (Th3), a turbidity value lower than a threshold value (Th1) during normal output operation described later is set in the control unit 20 in advance.

  If the amount of turbidity contained in the raw water (raw water turbidity TU) is not less than a preset threshold value (Th3) in step S14 (step S14; NO), the control unit 20 stops air scrubbing. Since there is a high possibility that the operating pressure of the membrane module 4 will rise, the blower b1 is maintained in an activated state, and the process proceeds to step S16.

  On the other hand, if the amount of turbidity contained in the raw water (raw water turbidity TU) is less than a preset threshold value (Th3) in step S14 (step S14; YES), the control unit 20 performs air scrubbing. Since it is unlikely that the operating pressure of the membrane module 4 will increase due to the suspension of the process, the process proceeds to step S15 in order to stop the air scrubbing.

  And the control part 20 stops the blower b1, and stops the air scrubbing of the membrane module 4 (step S15). In this way, the operation and stop of the blower b1 are controlled independently of the switching between the filtration process and the backwash process, and the amount of turbidity contained in the raw water is reduced to a low level of the threshold (Th3). When the water treatment method ends physical cleaning of the membrane surface of the membrane module 4, the power cost of the blower b1 is kept to a minimum while always maintaining the operating pressure of the membrane module 4 within an appropriate range. Can do.

  Next, the control unit 20 determines whether or not the amount of turbidity contained in the raw water (raw water turbidity TU) is greater than or equal to a preset threshold (Th1) (step S16). As the threshold value (Th1), for example, a turbidity value that is expected to cause clogging of the separation membrane and difficulty in continuing stable filtration processing is set in the control unit 20 in advance.

  If the amount of turbidity contained in the raw water (raw water turbidity TU) is not greater than or equal to a preset threshold value (Th1) in step S16 (step S16; NO), the control unit 20 enters the membrane separation tank 3. Since it is possible to prevent the turbidity from being excessively concentrated with the normal drainage amount F1, the process proceeds to step S17.

  And the control part 20 performs control which switches the drainage pump P2 to a normal output (step S17). If the amount of turbidity concentrated in the membrane separation tank 3 is small, it is not necessary to draw a large amount of the retained water containing the turbidity from the membrane separation tank 3 to lower the recovered rate of filtered water. Therefore, the drainage pump P2 is controlled so as to perform a normal output operation with remaining power, and the flow rate of the accumulated water drained through the drainage channel 10 (drainage withdrawal amount F1) is usually in accordance with a desired recovery rate. Of amount.

  Subsequently, the control unit 20 stops the introduction of raw water, and activates the backwash pump P3 to start a backwash process for backwashing the membrane module 4 (step S18). During this backwash operation, the drainage pump P2 drains the staying water staying in the membrane separation tank 3 with a normal output, and the staying water that may be concentrated in turbidity is drained with a normal withdrawal amount. Is done. Then, when the backwash process for a predetermined time is performed, the backwash operation is finished, and the next filtration process is performed.

  On the other hand, if the amount of turbidity contained in the raw water (raw water turbidity TU) is greater than or equal to a preset threshold (Th1) in step S16 (step S16; YES), the control unit 20 performs membrane separation. Since it is not possible to prevent the turbidity from being excessively concentrated in the tank 3 with the normal drainage amount F1, the process proceeds to step S19.

  Next, the control unit 20 determines whether or not the amount of turbidity contained in the raw water (raw water turbidity TU) is equal to or greater than a preset threshold (Th2) (step S19). As the threshold value (Th2), a turbidity value higher than the threshold value (Th1) during normal output operation is preset in the control unit 20.

  If the amount of turbidity contained in the raw water (raw water turbidity TU) is not greater than or equal to a preset threshold value (Th2) (step S19; NO), the controller 20 in the membrane separation tank 3 in step S19. Since excessively concentrated turbidity can be prevented only by adjusting the drainage withdrawal amount F1, the process proceeds to step S20.

  And the control part 20 performs control which switches the waste_water | drain pump P2 to high output (step S20). If the amount of turbidity concentrated in the membrane separation tank 3 is large, it is necessary to reduce the operating pressure of the membrane module 4 by drawing a large amount of the suspended water containing turbidity from the membrane separation tank 3. Therefore, the drainage pump P2 is switched to a higher output operation than the normal output, and the flow rate of the accumulated water drained through the drainage channel 10 (drainage extraction amount F1) is increased to a larger amount than usual.

  Subsequently, the control unit 20 stops the introduction of raw water, and activates the backwash pump P3 to start a backwash process for backwashing the membrane module 4 (step S21). During this backwash operation, the drainage pump P2 drains the staying water staying in the membrane separation tank 3 with a higher withdrawal amount than usual. When the amount of turbidity contained in the raw water increases, if the water treatment method increases the flow rate of accumulated water drained through the drainage channel 10 (drainage withdrawal amount F1), the turbidity retained in the membrane separation tank 3 However, since the drainage extraction amount F1 is increased from the normal amount, the separation membrane included in the membrane module 4 is less likely to be clogged. Therefore, it is possible to continue the membrane filtration using the pressure difference due to the water level while maintaining the operating pressure of the membrane module 4 within an appropriate range. Then, when the backwash process for a predetermined time is performed, the backwash operation is finished, and the next filtration process is performed.

  On the other hand, when the amount of turbidity contained in the raw water (raw water turbidity TU) is greater than or equal to a preset threshold value (Th2) in step S19 (step S19; YES), the control unit 20 performs membrane separation. Since it is not possible to prevent the turbidity from being excessively concentrated in the tank 3 only by adjusting the drainage extraction amount F1, the process proceeds to step S22.

  And the control part 20 performs control which switches the drain pump P2 to a normal output, and operates the blower b1 (step S22). In a state where the amount of turbidity concentrated in the membrane separation tank 3 is particularly large, the separation membrane provided in the membrane module 4 is very likely to be clogged. Therefore, simply increasing the drainage withdrawal amount F1 The operating pressure cannot be reduced sufficiently. Therefore, the drain pump P2 is switched to a high output operation higher than the normal output, and the blower b1 for air scrubbing the membrane module 4 is activated.

  Subsequently, the control unit 20 stops the introduction of raw water, and activates the backwash pump P3 to start a backwash process for backwashing the membrane module 4 (step S23). During this backwash operation, the drainage pump P2 drains the staying water staying in the membrane separation tank 3 with a higher withdrawal amount than usual. The blower b1 performs air scrubbing by diffusing the membrane surface of the separation membrane provided in the membrane module 4. When the amount of turbidity contained in the raw water is increased, when the water treatment method starts physical cleaning of the membrane surface of the membrane module 4, the turbidity adhering to the separation membrane provided in the membrane module 4 is peeled off. Since it is removed, the separation membrane included in the membrane module 4 is less likely to be clogged. Therefore, it is possible to continue the membrane filtration using the pressure difference due to the water level while maintaining the operating pressure of the membrane module 4 within an appropriate range. Then, when the backwash process for a predetermined time is performed, the backwash operation is finished, and the next filtration process is performed.

  According to the operation method of the water treatment apparatus 100 described above, when the amount of turbidity contained in the raw water (raw water turbidity TU) is equal to or higher than a preset first threshold (Th1), the drainage channel 10 is used. Control is performed to increase the flow rate of accumulated water to be drained. Therefore, even if the quality of the raw water fluctuates and the amount of turbidity contained in the raw water increases, the turbidity staying in the membrane separation tank 3 is discharged, and the separation membrane provided in the membrane module 4 Clogging can be reduced. That is, since the increase in permeation resistance of the separation membrane is suppressed, it is possible to continue low-cost membrane filtration using a pressure difference due to the water level. Therefore, according to this operation method, it is possible to stably continue the immersion type membrane filtration at a low cost.

  Further, according to the operation method of the water treatment apparatus 100 described above, when the amount of turbidity contained in the raw water (raw water turbidity TU) is equal to or higher than a preset second threshold (Th2), the blower b1 Starts and air scrubbing of the membrane module 4 is started. Therefore, even if the quality of the raw water fluctuates and the amount of turbidity contained in the raw water increases extremely, clogging of the separation membrane provided in the membrane module 4 can be reduced. That is, since air scrubbing is performed in a timely manner, a pressure difference due to the water level can always be secured stably, and the power cost of the blower b1 can be minimized.

FIG. 3 is a flowchart showing an operation method related to filtered water of the water treatment apparatus according to the embodiment of the present invention.
As shown in FIG. 3, in the water treatment apparatus 100, the operation of the filtered water pump P <b> 1 that pumps the filtered water flowing through the filtered water channel 8 flows out of the membrane module 4 during the normal operation for performing the filtering treatment, and flows out of the filtered water channel 8. The flow rate is controlled based on the flow rate of filtered water (filtered water flow rate F2). By controlling the filtered water pump P1, the flow of the filtered water in the filtered water channel 8 is switched from a natural flow due to the water level to a forced transfer by the pump.

  When the operation of the water treatment apparatus 100 is started by a command from an operator or an operation program, the control unit 20 sets the filtered water flow rate adjustment valve 7 to an initial opening, and drains the accumulated water remaining in the membrane separation tank 3. The raw water is filtered using the water level difference (step S31). At the start of operation of the water treatment apparatus 100, the amount of turbidity concentrated in the membrane separation tank 3 is small, and the flow rate of accumulated water drained through the drainage channel 10 (drainage withdrawal amount F1) is a desired value. The amount is a normal amount corresponding to the recovery rate. Therefore, the filtered water flow rate adjustment valve 7 has a medium opening degree that matches the opening degree at the end of the previous filtration process and can be adjusted in the opening direction and the closing direction, for example. And the flow of the filtered water in the filtered water channel 8 becomes a flow by natural flow at an initial flow rate corresponding to a desired recovery rate.

  And the control part 20 refers to the quantity of the raw | natural water which is introduce | transduced into the membrane separation tank 3 and is subjected to the filtration process during the filtration process (step S32). The amount of raw water is measured at a predetermined cycle by a flow sensor (not shown) installed in the raw water channel 1, a water level sensor (not shown) installed in the membrane separation tank 3, and the like, and is input to the control unit 20.

  Subsequently, the control part 20 performs control which adjusts the opening degree of the filtrate water flow regulating valve 7 (step S33). For example, if the amount of raw water introduced into the membrane separation tank 3 and filtered is normal, the opening of the filtrate flow rate adjusting valve 7 is maintained at the initial opening to maintain the operating pressure. On the other hand, when there is a demand for producing filtered water at a high recovery rate, the opening degree of the filtered water flow rate adjusting valve 7 may be opened in the opening direction.

  Subsequently, the control unit 20 measures the flow rate of filtered water (filtered water flow rate F2) flowing through the filtered water channel 8 (step S34). The flow rate of filtered water (filtrated water flow rate F <b> 2) is measured by the filtered water flow rate sensor 6 at a predetermined cycle and input to the control unit 20.

Next, the control unit 20 determines whether or not the flow rate of filtered water flowing through the filtered water channel 8 (filtrated water flow rate F2) is less than a preset lower limit of flow rate (F _L ) (third threshold value) (step S35). . As the lower limit of flow rate (F _L ), for example, an arbitrary flow rate value within a range in which membrane filtration can be performed with a pressure difference due to only the water level is preset in the control unit 20.

If the flow rate of filtrate water (filtered water flow rate F2) flowing through the filtered water channel 8 is not less than the preset flow rate lower limit (F _L ) in step S35 (step S35; NO), the control unit 20 performs pressure based only on the water level. Since the membrane filtration can be continued by the difference, the process proceeds to step S36.

And the control part 20 adds the counter of elapsed time about the time (less than flow time t1) when the flow volume of filtrate water (filtered water flow volume F2) which flows through the filtered water channel 8 is less than a flow volume lower limit (F _L ). First, reset (step S36). Then, the control part 20 returns a process to step S32.

On the other hand, when the flow rate of the filtered water flowing through the filtered water channel 8 (filtrated water flow rate F2) is less than the preset lower limit of flow rate (F _L ) in Step S35 (Step S35; YES), the control unit 20 determines the water level. Since there is a possibility that the membrane filtration cannot be continued due to the pressure difference due to the pressure alone, the process proceeds to step S37.

And the control part 20 adds the counter of elapsed time about the time (less than flow time t1) when the flow volume (filtrated water flow volume F2) of the filtered water which flows through the filtered water channel 8 is less than a flow volume lower limit (F _L ). (Step S37). Thereafter, the control unit 20 advances the process to step S38.

Next, the control unit 20 sets in advance the integration of the counter for a time (less than flow time t1) in which the flow rate of the filtered water flowing through the filtered water channel 8 (filtered water flow rate F2) is less than the flow rate lower limit (F _L ). It is determined whether or not the threshold value (Th4) is exceeded (step S38). As the threshold (Th4), for example, a value is set in the control unit 20 in advance so that the integration of the counter for the sub-flow time t1 becomes a count corresponding to several seconds to several tens of seconds in real time. When the integration of the counter for the sub-flow time t1 reaches several seconds to several tens of seconds, the decrease in the flow rate of the filtered water (filtered water flow rate F2) is not a temporary phenomenon, and the required operating pressure is only the water level. This is because it can be determined that it is in a state where it cannot be ensured by.

In step S38, the control unit 20 integrates the counter for a time (less than flow time t1) in which the flow rate of filtered water flowing through the filtered water channel 8 (filtered water flow rate F2) is less than the flow rate lower limit (F _L ). If it is not equal to or greater than the preset threshold value (Th4) (step S38; NO), there is a high possibility that the flow rate of the filtered water (filtered water flow rate F2) is temporarily reduced, so the process returns to step S32.

On the other hand, in step S38, the control unit 20 integrates the counter for the time during which the flow rate of the filtered water flowing through the filtered water channel 8 (filtered water flow rate F2) is less than the lower limit of flow rate (F _L ) (less than flow time t1). However, if it is equal to or greater than the preset threshold value (Th4) (step S38; YES), there is a high possibility that the decrease in the flow rate of the filtered water (filtered water flow rate F2) is continuous, so the process proceeds to step S39. .

And the control part 20 starts the pumping of the filtered water which operates the filtered water pump P1 and flows through the filtered water channel 8 (step S39). Thus, when the integration of the time (less than flow time t1) during which the flow rate of filtrate water (filtered water flow rate F2) flowing through the filtered water channel 8 is less than the lower limit of flow rate (F _L ) is a predetermined value or more, When the water treatment method for operating the filtrate water pump P1 is performed, when the flow rate of the filtrate water (the filtrate water flow rate F2) is clearly reduced, the flow of the filtrate water in the filtrate water channel 8 is caused from the natural flow caused by the water level. It can be switched to forced transfer by a pump. Therefore, the power cost of the filtrate water pump P1 can be minimized and the operating pressure of the membrane module 4 can be maintained in an appropriate range.

  Subsequently, the control unit 20 measures the operating pressure (P) of the membrane module 4 while the filtered water pump P1 is operating (step S40). The operating pressure (P) of the membrane module 4 is measured at a predetermined cycle by a pressure sensor (not shown) that measures the pressure on the primary side and the secondary side of the separation membrane, and is input to the control unit 20.

Next, the control unit 20 determines whether or not the operating pressure (P) of the membrane module 4 is equal to or higher than a preset pressure lower limit (P _L ) (step S41). As the pressure lower limit (P _L ), for example, a pressure value in the vicinity of the minimum water level difference at which membrane filtration can be performed with a pressure difference due to only the water level, or a value of −80 kPa or more depending on the performance of the membrane module 4 is used. , Preset in the control unit 20.

When the operating pressure (P) of the membrane module 4 is not equal to or higher than the preset lower pressure limit (P _L ) (step S41; NO), the control unit 20 supplements the operating pressure with the filtrate water pump P1 in step S41. Since it is necessary to continue, the process proceeds to step S42.

Then, the control unit 20 resets the elapsed time (pressure excess time t2) during which the operating pressure (P) of the membrane module 4 is equal to or higher than the pressure lower limit (P _L ) without adding the elapsed time counter (step S42). ). Then, the control part 20 returns a process to step S40.

On the other hand, when the operating pressure (P) of the membrane module 4 is equal to or higher than the preset pressure lower limit (P _L ) in step S41 (step S41; YES), the control unit 20 uses the filtered water pump P1 to operate the operating pressure. Therefore, the process proceeds to step S43.

Then, the control unit 20, the operating pressure of the membrane module 4 (P) is the lower pressure limit _{(P L)} or more and going on time (pressure overtime t2), adds the counter of elapsed time (step S43). Then, the control part 20 advances a process to step S44.

Next, the control unit 20 adds the counter to the preset threshold value (Th5) for the time (pressure excess time t2) when the operating pressure (P) of the membrane module 4 is equal to or higher than the pressure lower limit (P _L ). It is determined whether or not this is the case (step S44). As the threshold value (Th5), for example, a value is set in the control unit 20 in advance so that the integration of the counter for the pressure excess time t2 becomes a count corresponding to several seconds to several hours in real time. This is because, when the integration of the counter for the overpressure time t2 reaches several hours to several hours, it can be determined that the membrane can be stably recovered by the pressure difference due to the water level alone.

In step S44, the control unit 20 determines the integration of the counter for the time (pressure excess time t2) during which the operating pressure (P) of the membrane module 4 is equal to or higher than the pressure lower limit (P _L ). If not (Th5) or more (step S44; NO), there is a high possibility that the operating pressure has risen sufficiently and is not stable, so the process returns to step S41.

On the other hand, in step S44, the control unit 20 sets in advance the integration of the counter for the time (pressure excess time t2) when the operating pressure (P) of the membrane module 4 is equal to or higher than the pressure lower limit (P _L ). If it is equal to or greater than the threshold value (Th5) (step S44; YES), it is highly possible that the operating pressure has risen sufficiently and is stable, and thus the process proceeds to step S45.

And the control part 20 stops the filtered water pump P1, and complete | finishes the pumping of the filtered water which flows through the filtered water channel 8 (step S45). Thus, when the integration of the time (pressure excess time t2) during which the operating pressure (P) of the membrane module 4 is equal to or higher than the pressure lower limit (P _L ) becomes equal to or greater than a predetermined value, the filtered water pump P1 is stopped. When the operating pressure (P) of the membrane module 4 is stabilized, the flow of the filtered water in the filtered water channel 8 can be switched from the forced transfer by the pump to the natural flow by the water level. . Therefore, the power cost of the filtrate water pump P1 can be suppressed while maintaining the operating pressure of the membrane module 4 within an appropriate range.

  Thereafter, when the filtered water pump P1 is stopped, the control unit 20 returns the processing, and continues the filtration processing by membrane filtration with a pressure difference due to only the water level. The filtration process by the membrane module 4 ends when the control unit 20 receives an operation stop command instructed by an operator or an operation program. And after the back washing process of the membrane module 4 is performed, the next filtration process is implemented or the driving | operation of the water treatment apparatus 100 is stopped.

According to the operation method of the water treatment apparatus 100 described above, when the flow rate of the filtrate water flowing through the filtration water channel 8 (filtrated water flow rate F2) is less than a preset flow rate lower limit (F _L ) (third threshold value), Control for operating the filtered water pump P1 is performed. Therefore, the water quality of raw water fluctuates, the amount of turbidity contained in the raw water increases, the water temperature of the raw water decreases, and the permeation resistance of the separation membrane provided in the membrane module 4 increases. Even if the flow rate of filtered water is reduced by this, it is possible to quickly shift from membrane filtration using a pressure difference due to only the water level to membrane filtration using power. In other words, even when a situation in which the operating pressure decreases while performing low-cost membrane filtration using a pressure difference due to the water level, membrane filtration is performed without stopping the operation of the water treatment apparatus 100. It is possible to continue. Therefore, according to this operation method, it is possible to stably continue the immersion type membrane filtration at a low cost.

Further, according to the operation method of the water treatment apparatus 100 described above, when the operation pressure (P) of the membrane module 4 becomes equal to or higher than a preset pressure lower limit (P _L ), the control to stop the filtrate water pump P1 is performed. Done. That is, the time when the flow of the filtered water in the filtered water channel 8 is switched from the forced transfer by the pump to the natural flow by the water level is determined by the operating pressure (P). Therefore, based on the operating pressure (P), it is ensured that the permeation resistance of the separation membrane included in the membrane module 4 is in an acceptable range, and that the separation membrane is in a healthy state that is not damaged, etc. Membrane filtration can be continued stably.

FIG. 4 is a flowchart showing another example of the operation method related to the filtered water of the water treatment apparatus according to the embodiment of the present invention.
As shown in FIG. 4, in the operation of the water treatment apparatus 100, the operation of the filtered water pump P <b> 1 that pumps the filtered water flowing through the filtered water channel 8 during the normal operation for performing the filtration treatment is performed. Instead of the flow rate (filtrated water flow rate F2), control can also be performed based on the operating pressure (P) of the membrane module 4.

  When the operation of the water treatment apparatus 100 is started by a command from the operator or the operation program, the control unit 20 performs the filtration process with the filtered water flow rate adjustment valve 7 as the initial opening degree, similarly to the operation method shown in FIG. It starts (step S31), refers to the amount of raw water introduced into the membrane separation tank 3 and filtered (step S32), and performs control to adjust the opening of the filtrate flow rate adjusting valve 7 (step S33).

  Subsequently, the control unit 20 measures the operating pressure (P) of the membrane module 4 after the opening degree of the filtrate flow rate adjusting valve 7 is controlled (step S54). The operating pressure (P) of the membrane module 4 is measured at a predetermined cycle by a pressure sensor (not shown) that measures the pressure on the primary side and the secondary side of the separation membrane, and is input to the control unit 20.

Next, the control unit 20 determines whether or not the operating pressure (P) of the membrane module 4 is less than a preset pressure lower limit (P _L ) (step S55). As the pressure lower limit (P _L ), for example, a pressure value in the vicinity of the minimum water level difference at which membrane filtration can be performed with a pressure difference due to only the water level, or a value of −80 kPa or more depending on the performance of the membrane module 4 is used. , Preset in the control unit 20.

If the operating pressure (P) of the membrane module 4 is not less than the preset lower pressure limit (P _L ) in step S55 (step S55; NO), the control unit 20 continues the membrane filtration with a pressure difference based only on the water level. Therefore, the process returns to step S32.

On the other hand, when the operation pressure (P) of the membrane module 4 is less than the preset lower pressure limit (P _L ) (step S55; YES), the control unit 20 determines that the membrane pressure difference with only the water level is the membrane. Since filtration cannot be continued, the process proceeds to step S39.

Thereafter, similarly to the operation method shown in FIG. 3, the control unit 20 operates the filtered water pump P1 to start pumping the filtered water flowing through the filtered water channel 8 (step S39), and the operating pressure (P ), The filtered water pump P1 is stopped (step S45), and the filtration process by membrane filtration is continued. Note that when operating the filtration water pump P1 to the pressure lower limit of (step S55) _{(P L),} when stopping the filtrate pump P1 pressure lower limit of (step S41) _{(P L),} even though same value It is good also as a mutually different value.

According to the operation method of the water treatment apparatus 100 described above, when the operation pressure (P) of the membrane module 4 becomes less than a preset pressure lower limit (P _L ), control for operating the filtered water pump P1 is performed. . Therefore, the permeation resistance of the separation membrane included in the membrane module 4 is increased due to fluctuations in the quality of the raw water, an increase in the amount of turbidity contained in the raw water, or a decrease in the water temperature of the raw water. However, regardless of the amount of raw water introduced or the amount of drained water withdrawn, it is possible to quickly shift from membrane filtration using a pressure difference due to water level alone to membrane filtration using power. In other words, even when a situation in which the operating pressure decreases while performing low-cost membrane filtration using a pressure difference due to the water level, membrane filtration is performed without stopping the operation of the water treatment apparatus 100. It is possible to continue. Therefore, according to this operation method, it is possible to stably continue the immersion type membrane filtration at a low cost.

  Next, a water treatment device and a water treatment method according to a modification of the present invention will be described.

FIG. 5 is a schematic diagram showing a schematic configuration of a water treatment apparatus according to a modification of the present invention.
As shown in FIG. 5, the water treatment apparatus 200 according to the modification includes a membrane separation tank (water tank) 3, a membrane module 4, and the like, similar to the water treatment apparatus 100 described above. In addition, in FIG. 5, illustration is abbreviate | omitted about the structure of the downstream of the filtration water channel 8. FIG. The water treatment device 200 according to the modification differs from the water treatment device 100 in that the raw water channel (1) for supplying raw water to the membrane separation tank 3 is composed of the coagulation sedimentation treatment system 1a and the bypass channel 1b. It is configured, and according to the amount of turbidity contained in the raw water, it is possible to switch between performing and not performing the coagulation sedimentation treatment.

  The coagulation sedimentation treatment system 1a is provided with a mixing basin 22, a flock formation basin 23, and a sedimentation basin 24 in this order downstream of the landing well 21 that receives the raw water supplied from the water source and upstream of the membrane separation tank 3. Is configured. On the other hand, the bypass channel 1b connects the landing well 21 and the membrane separation tank 3 by bypassing the coagulation sedimentation treatment system 1a. A switching valve V1 is provided downstream of the landing well 21, so that the path until the raw water flows into the membrane separation tank 3 is switched to either the path through the coagulation sedimentation treatment system 1a or the bypass path 1b. It has become.

  The mixing basin 22 is a treatment tank for mixing a flocculant that aggregates turbidity with raw water. The mixing basin 22 is provided with a stirring device 22a for rapidly stirring the raw water and a flocculant tank 22b capable of adding the flocculant to the raw water. When the raw water flowing into the mixing basin 22 contains a large amount of turbidity, the flocculant is added from the flocculant tank 22b and rapidly stirred by the stirrer 22a. A flock is formed. As the flocculant, for example, an aluminum flocculant such as a sulfate band or polyaluminum chloride, an iron flocculant such as iron chloride or iron sulfate, or a polymer flocculant is used.

  The flock formation pond 23 is a treatment tank for forming coarse flocs in the turbidity contained in the raw water. The flock formation pond 23 is equipped with, for example, a stirring device that gently stirs raw water. When the raw water that has flowed into the floc formation pond 23 is gently stirred, a coarse floc is formed in which minute flocs aggregate and easily settle. In addition, as means for slowly stirring the raw water, a bypass wall for bypassing the raw water, a rectifying plate, or the like may be provided instead of the stirring device.

  The sedimentation basin 24 is a treatment tank for sedimenting and separating coarse flocs from raw water. The sedimentation basin 24 is provided with, for example, a scraper that scrapes the settled flocs, an inclined plate or an inclined pipe that enlarges the sedimentation area and promotes sedimentation. Coarse flocs settle and separate from the raw water flowing into the sedimentation basin 24, and the flocs deposited on the bottom of the sedimentation basin 24 are scraped and discarded by a scraper. On the other hand, the supernatant raw water from which the floc has been removed is collected from the water collection trough and introduced into the membrane separation tank 3 in a state where the amount of turbidity is reduced.

FIG. 6 is a flowchart showing an operation method related to staying water in a water treatment apparatus according to a modification of the present invention.
As shown in FIG. 6, in the water treatment apparatus 200, the direction of the flow path by the switching valve V1 is determined based on the amount of turbidity contained in the raw water (raw water turbidity TU) during normal operation for filtration. Control. By controlling the switching valve V1, the path of the raw water introduced into the membrane separation tank 3 is switched to either the path passing through the coagulation sedimentation treatment system 1a or the bypass path 1b.

  When the operation of the water treatment apparatus 200 is started by a command from an operator or an operation program, the control unit 20 starts to introduce new raw water toward the membrane separation tank 3 as in the operation method shown in FIG. (Step S11).

  Then, the control unit 20 measures the amount of turbidity (raw water turbidity TU) contained in the raw water while the raw water is being introduced (step S61). The amount of turbidity contained in the raw water (raw water turbidity TU) is measured at a predetermined cycle by the turbidity sensor 2 and input to the control unit 20.

  In FIG. 6, the turbidity sensor 2 is installed immediately before the membrane separation tank 3, but may be installed in the tank of the landing well 21 or upstream of the landing well 21. Further, it may be used by being installed both immediately before the membrane separation tank 3, in the tank of the landing well 21, and upstream of the landing well 21. If it is installed immediately before the membrane separation tank 3, the switching valve V <b> 1 is adjusted for adjustment of the flow rate of retained water (drainage withdrawal amount F <b> 1), or in the tank of the landing well 21 or on the upstream side of the landing well 21. As for switching, the immediate response to fluctuations in turbidity is improved.

  Subsequently, similarly to the operation method shown in FIG. 2, the control unit 20 determines whether or not the blower b1 is operating (step S13), and the amount of turbidity contained in the raw water (raw water turbidity TU). ) Is less than a preset threshold (Th3) (step S14). If it is not less than the threshold value (Th3) (step S14; NO), the blower b1 is maintained in an activated state, and if it is less than the threshold value (Th3) (step S14; YES), the blower b1 is stopped.

Next, the control unit 20 determines whether or not the amount of turbidity contained in the raw water (raw water turbidity TU) is greater than or equal to a preset turbidity upper limit (TU _U ) (fourth threshold value) (step) S62). As the turbidity upper limit (TU _U ), for example, a turbidity value higher than a threshold value (Th3) during air scrubbing operation is set in the control unit 20 in advance.

If the amount of turbidity contained in the raw water (raw water turbidity TU) is not equal to or higher than the preset turbidity upper limit (TU _U ) (step S62; NO), the control unit 20 determines the raw water in step S62. Since it is not necessary to pre-process with the coagulation sedimentation processing system 1a, the process proceeds to step S63.

  And the control part 20 controls the switching valve V1, closes the flow path to the coagulation sedimentation processing system 1a, and opens the flow path to the bypass path 1b (step S63). Then, the control part 20 advances a process to step S12.

On the other hand, in step S62, the control unit 20 determines that the amount of turbidity contained in the raw water (raw water turbidity TU) is greater than or equal to a preset turbidity upper limit (TU _U ) (step S62; YES). Since the raw water needs to be pretreated with the coagulation sedimentation treatment system 1a, the process proceeds to step S64.

  And the control part 20 controls the switching valve V1, opens the flow path to the coagulation sedimentation processing system 1a, and closes the flow path to the bypass path 1b (step S64). Then, the control part 20 advances a process to step S65.

  Next, the control unit 20 executes control for performing the coagulation sedimentation process in the coagulation sedimentation processing system 1a (step S65). For example, the agitator 22a, the flocculant tank 22b, and the like are operated, and a pump (not shown) that transfers the water to be treated for the coagulation sedimentation process is operated. Then, the control part 20 advances a process to step S12.

  Then, the control part 20 continues the filtration process by membrane filtration similarly to the driving | running method shown in FIG. The filtration process by the membrane module 4 ends when the control unit 20 receives an operation stop command instructed by an operator or an operation program. And after the back washing process of the membrane module 4 is performed, the next filtration process is implemented or the driving | operation of the water treatment apparatus 100 is stopped.

According to the operation method of the water treatment apparatus 200 described above, the amount of turbidity contained in the raw water (raw water turbidity TU) is equal to or higher than a preset turbidity upper limit (TU _U ) (fourth threshold). When the raw water is coagulated and settled in the coagulation sedimentation processing system 1a and becomes less than the turbidity upper limit (TU _U ) (fourth threshold), the coagulation sedimentation processing system 1a is bypassed. Therefore, even if the quality of the raw water fluctuates and the amount of turbidity contained in the raw water increases extremely, the turbidity contained in the raw water is reduced by coagulation sedimentation, and then the pressure difference due to the water level is used. Thus, it is possible to perform low-cost membrane filtration. Moreover, since the frequency of the high output operation of the drainage pump P2 and the air scrubbing operation by the blower b1 is reduced, the power cost can be kept low. Therefore, according to this operation method, it is possible to stably continue the immersion type membrane filtration at a low cost.

  Although the present invention has been described above, the present invention is not limited to the above-described embodiments and modifications, and various modifications can be made without departing from the spirit of the present invention. For example, the present invention is not necessarily limited to the one having all the configurations included in the above-described embodiments and modifications. A part of the configuration of the embodiment or the modified example is replaced with another configuration, a part of the configuration of the embodiment or the modified example is added to another configuration, or a part of the configuration of the embodiment or the modified example is omitted. Can be.

  For example, in the water treatment apparatuses 100 and 200, the amount of turbidity contained in the raw water is measured by the turbidity sensor 2 installed in the raw water channel 1, and the determination of the amount of turbidity is turbidity. It is done by value. However, the turbidity sensor 2 may be installed in the membrane separation tank 3. The determination of the amount of turbidity may be made based on the light intensity value of transmitted light or scattered light, an image analysis value obtained by imaging raw water, or the like. Moreover, you may carry out with any of the measured instantaneous value and the integrated value of a predetermined period.

  In the water treatment apparatuses 100 and 200, the amount of turbidity contained in the raw water is measured as the turbidity of the raw water (raw water turbidity TU). However, the amount of turbidity contained in raw water is the total organic carbon (TOC), manganese or manganese compound concentration, iron or iron compound concentration, total nitrogen content, total phosphorus content, dissolved oxygen. It may be indirectly measured as an amount, a chemical oxygen demand, a biological oxygen demand, an oxidation reduction potential (ORP), or the like. However, from the viewpoint of correlation with the amount of turbidity and ease of measurement, the amount of turbidity contained in the raw water is preferably measured as turbidity or the amount of organic carbon.

  Further, in the water treatment apparatuses 100 and 200, the membrane separation tank 3 is connected to the drainage channel 10 provided with the drainage pump P2, and the drainage channel 10 drains the accumulated water staying in the membrane separation tank 3 to the drainage pump. It is provided so that it can be drained by the operation of P2. However, the membrane separation tank 3 may be configured to drain the accumulated water by natural flow using the height difference. In the drainage channel 10 that drains the staying water by natural flow, a staying water flow rate adjustment valve that can adjust the flow rate of the staying water may be installed as a flow rate adjusting device instead of the drainage pump P2.

1 Raw water channel 1a Coagulation sedimentation treatment system 1b Bypass channel 2 Turbidity sensor (water quality sensor)
3 Membrane separation tank (water tank)
4 Membrane module 5 Air supply pipe 6 Filtration water flow rate sensor 7 Filtration water flow rate adjustment valve (flow rate adjustment valve)
8 Filtration channel 9 Drainage flow sensor 10 Drainage channel 12 Filtration water tank 13 Backwash water supply pipe 14 Deaeration tank 15 Deaeration pipe 20 Control part 21 Landing well 22 Mixing pond 22a Stirring device 22b Flocculant tank 23 Flock formation pond 24 Sedimentation basin 100 Water treatment device 200 Water treatment device b1 Blower P1 Filtration water pump P2 Drainage pump (flow rate adjustment device)
P3 Backwash pump P4 Vacuum pump V1 selector valve

Claims (7)

A tank in which raw water is introduced;
A membrane module that is retained in the water tank so as to be immersed in water, and makes filtered water by filtering the raw water,
A drainage channel capable of draining the stagnant water staying in the water tank;
A flow rate adjustment device capable of adjusting the flow rate of the staying water drained through the drainage channel;
A water quality sensor for measuring the quality of the raw water;
A control unit for controlling the flow rate adjusting device based on measurement by the water quality sensor,
The said control part is the said accumulated water drained through the said drainage channel, when the quantity of the turbidity contained in the said raw | natural water calculated | required by the measurement by the said water quality sensor is more than the preset 1st threshold value Water treatment device that increases flow rate. A blower that diffuses and physically cleans the membrane surface of the membrane module,
The water treatment device according to claim 1, wherein the control unit starts the blower when the amount of turbidity contained in the raw water is equal to or greater than a preset second threshold value. A backwash pump for supplying backwash water to the membrane module for backwashing the membrane surface of the membrane module;
The said control part is a water treatment apparatus of Claim 1 or Claim 2 which drains the stagnant water which retains in the said water tank at the time of the action | operation of the said backwash pump through the said drainage channel.   The water treatment apparatus according to any one of claims 1 to 3, wherein the amount of turbidity contained in the raw water is measured as turbidity or organic carbon content. A filtered water tank that is provided with a water level with respect to the water tank and receives the filtered water made of the membrane module;
A filtration channel that connects between the membrane module and the filtered water tank, and allows the filtered water produced by the membrane module to flow down naturally into the filtered water tank;
A flow rate adjustment valve capable of adjusting the flow rate of the filtered water flowing through the filtered water channel;
A filtered water pump capable of pumping the filtered water flowing through the filtered water channel to the filtered water tank;
The said control part operates the said filtered water pump when the flow volume of the said filtered water which flows through the said filtered water channel becomes less than the preset 3rd threshold value. The water treatment apparatus as described.   When the amount of turbidity contained in the raw water is equal to or greater than a preset fourth threshold value, the raw water is introduced into the water tank after being subjected to coagulation sedimentation treatment. The water treatment apparatus according to item. A tank in which raw water is introduced;
A separation membrane that is retained in the water tank so as to be immersed in water, and filters the raw water to produce filtrate.
A drainage channel capable of draining the stagnant water staying in the water tank;
In a water treatment device comprising:
Filtering the raw water using the difference in water level while draining the stagnant water staying in the water tank,
A water treatment method for increasing the amount of the accumulated water drained through the drainage channel when the amount of turbidity contained in the raw water is increased.

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